An F-18 takes off from the US Navy’s USS Dwight D. Eisenhower to carry out airstrikes in Syria on July 7, 2016. (AFP photo)

The Pentagon has warned Syria and Russia that the US is ready to shoot down their planes, which Washington claims threaten American advisers in northern Syria.

The warning came after US fighter jets tried to engage Syrian Arab Air Force aircraft in Syria last week, but the showdown was avoided as government planes left before the Americans arrived.

Pentagon spokesman Captain Jeff Davis claimed on Friday the US fighters attempted to intercept the Syrian planes to protect American advisers – a term the US military often uses for its Special Operations Forces – working with Kurdish forces after the Syrian government jets bombed the area.

On Monday, another Pentagon spokesman, Peter Cook, said, “We would continue to advise the Syrian regime to steer clear of those areas.”

“We are going to defend our people on the ground, and do what we need to defend them,” Cook told reporters.

“It’s not a no-fly zone,” he said, adding that “the Syrian regime would be wise to avoid areas where coalition forces have been operating.”

When asked about Russia, Cook said the US would also do the same with Russian jets, which have been striking Daesh targets in Syria at the country’s request since last year.

“If they threaten US forces, we always have the right to defend our forces,” Cook said.

A screen grab taken from footage provided by Russian Defense Ministry on Nov. 2, 2015 shows a target hit during an air raid in Syria. (AP photo)

Russia launched its air offensive in Syria in September 2015. According to analysts, the campaign has so far broken the backbone of Daesh and other militants there, and has provided the Syrian government with an opportunity to defeat the foreign-sponsored terrorist onslaught.

The US and some of its Arab allies began their campaign in Syria in September 2014 without any authorization from Damascus or a UN mandate.

Since then, they have been carrying out airstrikes in the war-torn country, but their air raids have done little to stop the Takfiri group’s advances there.

Smoke and flames rise over the Syrian town of Kobani after a coalition airstrike on Oct. 20, 2014. (Reuters photo)

Davis said Friday that two Syrian SU-24 attack planes attacked Kurdish forces undergoing training with US Special Operations troops around the northeastern city of Hasakah, but they had left by the time the American jets arrived.

In response, the General Command of the Syrian Arab Army said later in the day that Kurdish forces were “attacking state institutions, stealing oil and cotton, obstructing exams, kidnapping unarmed civilians and spreading chaos and instability.”

Since March 2011, Syria has been gripped by a foreign-backed militancy. Daesh terrorists still control parts of Syria and Iraq.